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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
*/
package conn
import (
"net/netip"
"unsafe"
"golang.org/x/sys/unix"
)
// getSrcFromControl parses the control for PKTINFO and if found updates ep with
// the source information found.
func getSrcFromControl(control []byte, ep *StdNetEndpoint) {
ep.ClearSrc()
var (
hdr unix.Cmsghdr
data []byte
rem []byte = control
err error
)
for len(rem) > unix.SizeofCmsghdr {
hdr, data, rem, err = unix.ParseOneSocketControlMessage(rem)
if err != nil {
return
}
if hdr.Level == unix.IPPROTO_IP &&
hdr.Type == unix.IP_PKTINFO {
info := pktInfoFromBuf[unix.Inet4Pktinfo](data)
ep.src.Addr = netip.AddrFrom4(info.Spec_dst)
ep.src.ifidx = info.Ifindex
return
}
if hdr.Level == unix.IPPROTO_IPV6 &&
hdr.Type == unix.IPV6_PKTINFO {
info := pktInfoFromBuf[unix.Inet6Pktinfo](data)
ep.src.Addr = netip.AddrFrom16(info.Addr)
ep.src.ifidx = int32(info.Ifindex)
return
}
}
}
// pktInfoFromBuf returns type T populated from the provided buf via copy(). It
// panics if buf is of insufficient size.
func pktInfoFromBuf[T unix.Inet4Pktinfo | unix.Inet6Pktinfo](buf []byte) (t T) {
size := int(unsafe.Sizeof(t))
if len(buf) < size {
panic("pktInfoFromBuf: buffer too small")
}
copy(unsafe.Slice((*byte)(unsafe.Pointer(&t)), size), buf)
return t
}
// setSrcControl sets an IP{V6}_PKTINFO in control based on the source address
// and source ifindex found in ep. control's len will be set to 0 in the event
// that ep is a default value.
func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
*control = (*control)[:cap(*control)]
if len(*control) < int(unsafe.Sizeof(unix.Cmsghdr{})) {
*control = (*control)[:0]
return
}
if ep.src.ifidx == 0 && !ep.SrcIP().IsValid() {
*control = (*control)[:0]
return
}
if len(*control) < srcControlSize {
*control = (*control)[:0]
return
}
hdr := (*unix.Cmsghdr)(unsafe.Pointer(&(*control)[0]))
if ep.SrcIP().Is4() {
hdr.Level = unix.IPPROTO_IP
hdr.Type = unix.IP_PKTINFO
hdr.SetLen(unix.CmsgLen(unix.SizeofInet4Pktinfo))
info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&(*control)[unix.SizeofCmsghdr]))
info.Ifindex = ep.src.ifidx
if ep.SrcIP().IsValid() {
info.Spec_dst = ep.SrcIP().As4()
}
*control = (*control)[:unix.CmsgSpace(unix.SizeofInet4Pktinfo)]
} else {
hdr.Level = unix.IPPROTO_IPV6
hdr.Type = unix.IPV6_PKTINFO
hdr.SetLen(unix.CmsgLen(unix.SizeofInet6Pktinfo))
info := (*unix.Inet6Pktinfo)(unsafe.Pointer(&(*control)[unix.SizeofCmsghdr]))
info.Ifindex = uint32(ep.src.ifidx)
if ep.SrcIP().IsValid() {
info.Addr = ep.SrcIP().As16()
}
*control = (*control)[:unix.CmsgSpace(unix.SizeofInet6Pktinfo)]
}
}
var srcControlSize = unix.CmsgSpace(unix.SizeofInet6Pktinfo)
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